Bonfire of the Superweeds
In the Sonoran Desert, good intentions combust
For years, the scientists watched it spread. On Tumamoc Hill, a research preserve on the western edge of Tucson, botanists noted the first sprigs in 1968. The tousle-headed pasture grass, an import from Africa and Asia, gradually filled the open spaces between native plants. Below the spiky, succulent latticework of the Sonoran Desert - a landscape unaccustomed to fire - buffelgrass formed a thick carpet. A flammable carpet. The scientists watched, as they had been trained to do. But they also started to worry.
One day in 2005, U.S. Geological Survey researcher Julio Betancourt drove the winding, narrow road through the research preserve. Betancourt - an expert on the ancient climates of the Southwest - has made Tumamoc Hill his professional home for 26 years, and both the drive and the surrounding landscape were deeply familiar.
He paused at a hairpin turn and looked out at a steep, rocky hillside dotted with saguaro cacti, palo verde trees, and the rest of the botanical cast of the Sonoran Desert. Once again, he noticed the golden thickets of dry grass. But this time, Betancourt realized that buffelgrass was poised to win, no matter what.
"I realized I was looking at the very last saguaros on that landscape," he remembers, gesturing at the hillside. "We have saguaros embedded in an Africanized grassland. That's not normal." Whether or not a grass-fueled wildfire sweeps through the preserve, he points out, there's no longer enough space for the next generation of saguaros to begin their 150-year lifespans. "I realized that this was a microcosm of what was happening throughout the Sonoran Desert," he says. "This is one of the most impressive ecosystem conversions happening in North America."
Betancourt wasn't the first to notice the inexorable transformation
of the Sonoran Desert, and the threat to the city within it. But it
was his conviction - and his break with scientific convention -
that would give Tucson a fighting chance. "Buffelgrass is the worst
environmental crisis facing Tucson," he says flatly. "It's even
worse than development."
Some weeds arrive in our lives by accident. Buffelgrass came by invitation, riding on the pioneer dream of turning desert into pasture. Beginning in the late 1800s, ambitious agronomists carried buffelgrass from South Asia, Kenya and South Africa (buffel is Afrikaans for buffalo) to the Southern United States. It seemed the perfect grass for the Southwest: resistant to both drought and heat, tenacious enough to control erosion, bulky and nutritious enough for cattle feed. By the 1950s, ranchers in south Texas were planting it with abandon.
"Some ranchers down there swear by it," says Byron Burson, a plant geneticist with the federal Agricultural Research Service in College Station, Texas. "When they've had severe droughts, its tolerance has kept some of them in business."
In the 1960s and early 1970s, during the Green Revolution, Mexico was eager to enrich its portion of the Sonoran Desert, and buffelgrass seemed the ideal tool. With the encouragement of Mexican scientists, some trained in the United States, the Mexican federal government subsidized a buffelgrass planting spree. Ranchers in northwestern Mexico, who found that the wonder grass made their property values blossom, were glad to help it along.
"The bulldozing just took off like crazy," says David Yetman, a researcher at the University of Arizona with long experience in the Mexican state of Sonora. "They'd put a chain between two bulldozers and knock over all the trees - a lot of mesquite and a lot of ironwood, some of the finest trees in the world - and they would bulldoze them all into long rows."
The rows, called chorizos after the spicy Mexican sausage, were themselves a source of income: Ranchers often sold the wood to carboneros, who sold it to Mexican and U.S. steakhouses as premium mesquite charcoal. The charcoal trade funded more bulldozing, more buffelgrass planting, and eventually more steak for the steakhouses.
"I enjoy my carne asada," says Sonoran ecologist Alberto Burquez, "but I call it reprocessed buffelgrass."
The Sonoran bulldozing, which peaked in the 1980s and 1990s, has slowed now, more from lack of available land than lack of enthusiasm. Burquez, a professor at the Sonoran campus of the National Autonomous University of Mexico, estimates that direct buffelgrass plantings now cover 2.5 million acres of Sonora, an area larger than Yellowstone. "Most of the desert has been invaded by buffelgrass, and it's increasing," he says. Yet state and federal subsidy programs continue, good intentions unbowed. "In the past, they were described as programs for planting buffelgrass, creating grasslands, conquering the desert," Burquez says. "Today, they're called restoration or range improvement. They have these contorted names ... but it's like calling impotence erectile dysfunction. They still have incentives for planting buffelgrass."
Buffelgrass, which has few enemies, soon moved from these plantings into less disturbed desert. Its dense growth crowded out native seedlings and began to beat even large shrubs to water. When Arizona-Sonora Desert Museum ecologists Tom Van Devender and Mark Dimmitt studied buffelgrass stands in Arizona and Sonora, they found that both native annuals and short-lived perennials had virtually disappeared.
Buffelgrass also carries fire, an element all but unknown in the Sonoran Desert. Unlike native plants, it burns easily and recovers quickly, creating yet more fuel for more and bigger fires - and burying slow-growing cacti and shrubs beneath a spreading buffelgrass savannah.
To many desert ecologists, this cycle is all too familiar. Red brome, an invasive Mediterranean grass, also feeds a quickening cycle of fire and invasion in many parts of the Sonoran and Mojave Deserts. In the Mojave - another desert once believed to be all but fireproof - U.S. Geological Survey ecologist Todd Esque and his colleagues found that in burned areas, growth of red brome and other exotics consistently, and often dramatically, outpaced that of native annuals. Cheatgrass, another Mediterranean native, is ubiquitous in the Great Basin, where its ability to dominate burned areas frustrates efforts to restore native sagebrush.
Buffelgrass, however, has at least one advantage over its fellow desert invaders: While cheatgrass and red brome are annuals, fed by winter rains, buffelgrass is perennial. It responds to rainfall at almost any time of year, and bulks up as it sprouts and dries, able to fuel fires not just during a particular season but throughout the calendar. It can even flame up when green and by some estimates can burn at more than 1,300 degrees, literally hot enough to peel rocks.
In the 1940s, Burquez found, fires on the outskirts of the Mexican capital of Hermosillo were all but unknown. In the 1960s, newspapers began to report sporadic fires, and today, hundreds of fires break out on the edge of the city every year. "You see the very same patterns everywhere in arid Sonora," he says. The national telephone company lost so many poles to buffelgrass fires that it now sheathes its Sonoran poles in sleeves of sheet metal.
Today, the best fire protection
in Sonora comes on four legs. "If somehow cattle were to disappear,
we'd have a huge problem," says Burquez. Though cattle inspired the
planting of buffelgrass, their appetites also contain it and keep
Sonoran fires generally small, low to the ground, and easily
extinguishable. Without heavy pruning by cows, says Burquez,
buffelgrass would grow even denser and thicker, able to stoke still
hotter, higher, and more destructive fires. Just like in Tucson.
But we'll get to that in a minute.
In the early 1990s, from about 2,000 feet in the air, Sandra Lanham spotted the difference in the desert. Lanham was piloting her 1956 single-engine Cessna between her home in Tucson and northern Mexico, where she helps researchers survey endangered pronghorn, blue whales, and hundreds of other species. As she floated over the arid valleys of northern Sonora, she sighted something less charismatic, and more disturbing.
"I started to notice that the desert, in many, many places, was being bulldozed and planted," she says. "I knew something huge was going on, but I couldn't really see what was happening."
The bush pilot borrowed a video camera, which she handed to her passengers. "I literally didn't know how to turn it on," she says. She eventually collected footage not only from the air but also on the ground, showing bulldozers toppling columnar cacti like so many giant Gumby dolls.
Through flight after flight, Lanham saw that vast reaches of pale desert soil had been cleared and covered with buffelgrass. Once the native plants were felled and replaced, Lanham learned, they had little chance of recovery.
Working with a $500 budget, Lanham and her colleagues pieced their footage of the expanding pastures into an unvarnished 10-minute video. (A few years later, Lanham's work as an environmental pilot would win her a MacArthur Fellowship, but these were leaner times.) They made 125 copies and distributed them to potential converts in southern Arizona.
To many north of the border, the video was a shocking glimpse of an altered future. "I don't think anyone here recognized the scale of it," says Lanham. "I don't think they could have, unless they were flying in an airplane."
Buffelgrass seeds have long strayed across the international border, carried in tires, trade goods, or the clothing of illegal border crossers. But as in Texas and Mexico, buffelgrass was also invited into Arizona. From the 1940s until the 1980s, the federal Soil Conservation Service and other agencies planted the grass in test plots, where its unimpressive performance prevented more widespread introduction. Stuart Bengson, the former head of reclamation for ASARCO Inc., says the mining company used buffelgrass for erosion control at its copper mine south of Tucson until at least the late 1980s.
Buffelgrass did edge out of these original plantings and into native desert, but for years, the species was only a whisper in the desert ecosystem. Many biologists assumed it had little strength in the colder climes of southern Arizona.
"We thought that maybe (southern Arizona) wouldn't be like Sonora," says ecologist Van Devender, an expert on Sonoran Desert flora. In 1992, when he was working on a plant guide for the Tucson Mountains, "we had buffelgrass in there, but I remember writing that it wasn't very common, that it was just along roadsides," he says. "Well, right after that, it took off."
Sue Rutman, a botanist at Organ Pipe Cactus National Monument southwest of Tucson, says much of the blame for the buffelgrass boom lies with the climate. "Buffelgrass used to behave more like an annual grass in Arizona, because it would freeze in the winter," she says. "But with the warming trend we've had since the 1980s, there are fewer freezes, so buffelgrass has become this big bunchgrass that reproduces a lot more." The bigger the plant, the less vulnerable it is to freezing, and the more powerful its cycle of increased growth and increased spread.
Buffelgrass, once dismissed as a demure roadside weed, now grows throughout Tucson, in homeless camps and wealthy ridgetop neighborhoods. In a survey published last year, Van Devender and his colleagues found buffelgrass growing on nearly every unpaved city roadside, median and vacant lot, and radiating deep into the deserts of southern Arizona.
"Buffelgrass is like taking a kiddie pool, filling it with gas, and putting it in your front yard," says Kevin Kincaid, a fire inspector for Rural/Metro, a private emergency services provider. "These fires can go from four-foot flames to 30-foot flames in 20 seconds." Kincaid used to assure Tucson homeowners that the desert was fire resistant. He now says buffelgrass has fueled between 15 and 20 fires in the city within the past six weeks, and he's telling residents to protect their homes by pulling and spraying as much grass as they can. "Otherwise," he says, "it's grab the cat and run for your life."
Colder winters have kept buffelgrass at bay in southern
New Mexico, and low summer rainfall contains it in the California
deserts. But buffelgrass shows no such restraint in Arizona. In
Phoenix, 120 miles northwest of Tucson, the weed poses much the
same sort of fire threats as in the Tucson Basin. It grows at
elevations up to 5,300 feet in the Santa Catalina Mountains north
of Tucson, raising fears that the increasing number of desert fires
could jump into mountain forests. And on Tumamoc Hill, the research
preserve on the western limits of Tucson, Julio Betancourt is
watching a century-long tradition of botanical observation prepare
to go up in flames.
Betancourt joined a growing number of converts to the anti-buffelgrass cause. By the early 2000s, corps of volunteers and paid staff, inspired by Sue Rutman at Organ Pipe Cactus National Monument, had long been straining their backs pulling and spraying buffelgrass in Organ Pipe, Saguaro National Park, and Tucson Mountain Park. Land managers throughout southern Arizona were already on the alert, and a handful of scientists had been studying the species for years. Even so, buffelgrass was spreading further and further each year.
"I realized that there was no point in doing this piecemeal," says Betancourt. "I thought, 'This isn't going to work until we have a framework in place - until we act collaboratively in a way that I haven't seen Tucson, or Arizona, do with anything else.' "
His work began with an accident. When a gas pipeline ruptured within city limits in 2003, Kinder Morgan set about repairing its network of 1950s-era lines, one of which crossed Tumamoc Hill. With environmental mitigation money from that project and the help of an environmental fund established by a nearby resort, Betancourt hired a young plant ecologist named Travis Bean to help coordinate a countywide buffelgrass campaign - an effort Rutman would dub "Julio's buffelgrass jihad."
Betancourt's was an unusual undertaking for a scientist, especially a government scientist. Researchers are expected to collect data, present it, and leave the political tussle to others, just as most of those on Tumamoc Hill had for a century. To do otherwise often risks the censure of supervisors and colleagues. But Betancourt felt he had enough seniority - and cause - to challenge this tradition.
"I can understand the premise of being objective and non-advocacy, but if we follow that model in cases like buffelgrass, we can actually experience the unhinging of an ecosystem," he says. "We're the only people really standing in its way, and it's up to scientists to make sure that people understand what's at stake."
Betancourt's buffelgrass horror stories - delivered in a Texas-tinged baritone - did the job. Both he and Bean gave dozens of talks, describing the spread and impacts of buffelgrass to county officials, state representatives, homeowner's associations and resort developers. They put aside scientific talk of interspecies competition in the desert and took up the cry they believed everyone could understand: Fire!
Variations on their story - weeds, fire, big trouble - now echo throughout Tucson. "People come to Tucson for the desert and the scenery, and it's going to be changing," says state Rep. Olivia Cajero Bedford, D, whose homeowner's association hosted a buffelgrass talk. "Julio has opened a lot of our collective eyes," says Pima County economic development and tourism director Tom Moulton, who adds a booster's flourish: "We're a lot prettier than some of the other cities that have had trouble with it, so we have a lot more to lose." Under its Sonoran Desert Conservation Plan, the county is buying open space to protect wildlife habitat - a project that buffelgrass could well render meaningless.
Betancourt and Bean succeeded in convincing the state to add buffelgrass to its list of noxious weeds, a move that prohibits the import of seeds and plants and opens funding opportunities for local governments. Their forceful proposal met with only minor opposition.
Even buffelgrass itself helped the cause. Heavy rains in 2006 fed the invasion, and the yellow hillside carpets became obvious even to untrained eyes. Last fall, about 400 people volunteered to spend a day pulling buffelgrass in Sabino Canyon, a popular hiking spot in the foothills of the Santa Catalina Mountains. This past spring, Betancourt and Bean helped draw more than 100 people, including many federal, state and local officials, to a buffelgrass summit co-sponsored by Pima County. They're now pushing fire departments to publicize buffelgrass-fueled fires - currently categorized as "brush fires" - and continuing their efforts to pull and spray hundreds of acres of buffelgrass on and around Tumamoc Hill itself.
raised things to a frenetic level, and I'm not apologizing for
that," says Betancourt. "I think it's necessary."
Despite the press of local publicity and the well-established risks to safety, economy, and ecology, sustained commitment and funding for buffelgrass control is difficult to secure. With the weed racing into the desert - in some places, its reach is estimated to be doubling, sometimes tripling, each year - even Betancourt admits he finds it hard to be optimistic. "I'm skeptical that we can do anything about it," he says. "It's already far along, and it's moving very quickly. But we can't throw up our hands and say it's a done deal."
The best hope, perhaps, is that the Herculean efforts in Tucson will create more than a spasm of concern about one species, encouraging governments at all levels to get more serious and more strategic about weeds. Buffelgrass or its close relatives have already invaded many places around the world, including Hawaii, Australia, and South America, even reaching the Galapagos Islands. And buffelgrass isn't the first, or the last, exotic species to threaten entire ecosystems. As species invasions - encouraged by human travel, global trade and climate change - keep rising in number and severity, governments will increasingly be forced to choose from the worst of multiple threats.
"Every area of the state has a pressing problem," says Lori Faeth, environmental advisor to Arizona Gov. Janet Napolitano, D. Earlier this year, in response to the discovery of invasive quagga mussels in the Colorado River, the governor revived a statewide invasive species council. The group is devising a management plan for combating, containing and preventing invasions throughout the state, but won't complete it until mid-2008.
The National Invasive Species Council, an advisory group created by President Clinton in 1999, coordinates the federal response, but council executive director Lori Williams says much of the responsibility for dealing with particular species lies with state and local governments. "Invasive species are inherently hard to prioritize at a national level," she says, because they can pose very different threats in different places. The council does have a list of a half-dozen uber-invaders - such as tamarisk, the brown tree snake and Asian carp - that are considered national priorities, and Williams says buffelgrass may join that list. Because of the upwelling of local and state concern, she adds, "it's a good time for us to get involved and show support."
But not every superweed has a foe like Betancourt, and the next buffelgrass may already be making its way, largely unheralded, across the desert. Few, if any, scientists question the transformative power of buffelgrass, but some say Sahara mustard, another fire-carrying invasive weed, poses an even more serious threat, because of its ability to invade a wider range of habitats. All agree that more exotics are on the way.
"We're going to get hit with a big wave of Australian things," predicts Organ Pipe botanist Sue Rutman. Australia already has serious problems with North American species such as mesquite and willow, she says, and the United States is ripe for a reverse invasion. Rutman remembers driving by a plant nursery on I-10 that advertised landscaping plants from Down Under. "They had this big sign up saying, 'Australian plants! No worries!' " she says. "And I'm thinking, 'Yes! Big worries!' "
"We've got all these
other species in the pipeline, and we're going to have to deal with
those, too," says buffelgrass coordinator Travis Bean. "The desert
is no longer maintenance-free."
The Sonoran Desert still suffers from good intentions. Though buffelgrass is barred from Arizona's doorstep, fountaingrass, a close relative, remains a popular landscaping plant. Despite widespread warnings about the invasive nature of fountaingrass, it sits prettily on the shelves of Tucson's Home Depots, one man's weed posing as another man's decor.
Or pasture, as the case may be. To the horror of many in Tucson, state and federal agricultural agencies in Texas released a cold-tolerant variety of buffelgrass in early 1999. The grass strain, known as Frio, was a long-awaited boon for south Texas ranchers, who wanted a hardier grass that could survive winter storms. But for many southern Arizonans, a turbocharged version of the species was a nightmare come true. After complaints from scientists in Tucson, the federal Agricultural Research Service suspended its research on the "improvement" of buffelgrass.
"At that time, I didn't even know it was a problem in Arizona," says Byron Burson, whose lab selected the cold-tolerant strain from plants collected in South Africa. Frio has never been widely sold in Texas, but researchers report planting it in northern Mexico. How far it will spread remains unknown.
In 2000, alerted by Tucson scientists, members of the National Invasive Species Council met with the Agricultural Research Service about the development of the Frio strain. The council is now creating National Environmental Policy Act guidelines that would require federal agencies to consider invasive species issues. But for the moment, vigilant ecologists are the only barriers to another Frio.
When it comes to weeds, Burson points out, there's a deeper ambivalence yet to resolve. "If you don't have a grass with some invasiveness and some aggressiveness, you might as well not release it as a pasture grass, because it's not going to survive under grazing," he says. "We're trying to meet two groups' interests here. The ranchers want something that's aggressive, and the environmentalists don't want anything that's introduced."
Can he foresee any solution to that dilemma?
"Yeah," he says. "Retirement."
Michelle Nijhuis is a contributing editor of High Country News.
Botanist Sue Rutman has had surprising success just yanking up buffelgrass, but herbicides remain the first line of defense